Internet Protocol (IP) Multimedia Subsystem (IMS) networks play a key role in the transition from networks supporting circuit-switched communications to those providing packet-switched communications. Many telecommunications network providers have partially deployed IMS networks with only a subset of their subscribers being capable of utilizing the IMS networks, and only a portion of those capable being registered to do so.
Standard Bodies, such as the Third Generation Partnership Project (3GPP), however, assume in their specifications that all subscribers will be IMS registered. For example, 3GPP Specification 23.204 assumes that every user is an active IMS subscriber and states that all Send Routing Information for Short Message (SRI-SM) messages should be routed to an IP Short Message Gateway (IP-SM-GW), which then queries a Home Location Register (HLR) or Home Subscriber Server (HSS) via an additional SRI-SM. In a telecommunications network where not all of the subscribers have active IMS registrations, however, much of this messaging between an IP-SM-GW and the HLR/HSS will be unnecessary.